Can't really compare the two games like you can compare Torchlight to Diablo.
I personally really like the skill system for Path of Exile and the darker tone that actually evokes a better feel of DIablo II than Diablo III did. The possibilities of builds in Path of Exile are endless with their skill system, it's quite great.
I love Torchlight, but I'm going to have to say Path of Exile for long term enjoyment. It is an MMO after all. And Grinding Gears is planning to add new contents/Acts consistently --- http://i.imgur.com/kMixF.jpg http://imgur.com/pE5Me.jpg http://i.imgur.com/QY7Ig.jpg
The only non-speculative answer: Too early to tell for certain. It launches out of closed Beta I believe this Wednesday. --- If you don't like what a gaming company is trying to force upon you and the market, don't buy that company's games. Cruel DRM can only flourish if you let it.
i believe PoE has the original diablo feel, with a lot more freedom then this game has, but as a more casual friendly, and easily moddable game, torchlight 2 is superior, its just a choice of what you want to do.
The gameplay differences are mainly a matter of taste- TL2 is faster and more casual whilst POE is slower and tougher.
The only main advantage of POE over Tl2 is atmosphere- POE's is just brilliant, I can't think of a good analogue but it always feels like a doomed slog into a black and terrible abyss. --- "You're casual if you like anything. Real hardcore gamers hate everything." Cyhortl82